Image fo ming device and image forming method

Abstract

An image forming device for forming an image on an image carrier using a different grayscale reproduction method for each of two or more different attributes contained in portions of the image. The image forming device forms a different standard pattern in one-to-one correspondence with each different attribute contained in the image portions, using a grayscale reproduction method used for reproducing image portions containing the attribute, detects density of each standard pattern formed by the standard pattern forming unit, sets, for each different attribute, a condition for correcting grayscale of the image portions containing the attribute, in accordance with the detected density, and corrects grayscale of the image portions in accordance with each condition set by the correction condition setting unit.

1. An image forming device for forming an image on an image carrier using a different grayscale reproduction method for each of two or more different attributes contained in portions of the image, the image forming device comprising:
 a standard pattern forming unit operable to form a different standard pattern on an image carrier in one-to-one correspondence with each different attribute contained in the image portions, wherein the different patterns are each formed using a different grayscale reproduction method used for reproducing image portions containing the attribute; 
 a detecting unit comprising a sensor operable to detect density of each standard pattern formed by the standard pattern forming unit; 
 a correction condition setting unit operable to set, for each different attribute, a condition for correcting grayscale of the image portions containing the attribute, in accordance with the density detected by the detecting unit; and 
 a grayscale correcting unit comprising a processor operable to correct grayscale of the image portions on the image carrier in accordance with each condition set by the correction condition setting unit. 
 
     
     
       2. The image forming device of  claim 1 , wherein
 attributes contained in the image portions include an edge and a non-edge, and 
 the standard pattern forming unit forms, as a standard pattern, an edge pattern in accordance with a grayscale reproduction method that is used for reproducing edge portions of the image, and forms, as a standard pattern, a non-edge pattern in accordance with a grayscale reproduction method that is used for reproducing non-edge portions of the image. 
 
     
     
       3. The image forming device of  claim 2 , wherein
 the non-edge pattern includes a plurality of first patches, 
 the plurality of first patches have different grayscale levels and each first patch has a first area size, the edge pattern includes a plurality of second patches, and 
 the plurality of second patches have different grayscale levels and each second patch has a second area size that is smaller than the first area size. 
 
     
     
       4. The image forming device of  claim 3 , wherein
 the standard pattern forming unit forms the first patches and the second patches on the image carrier to be arranged in sequence such that respective patches of the first patches and the second patches are alternately adjacent to each other. 
 
     
     
       5. The image forming device of  claim 4 , wherein
 the standard pattern forming unit forms the first patches and the second patches such that in a direction in which the first patches and the second patches are arranged, grayscale of patches in each sequence of the first patches and the second patches becomes gradually higher from one end to another end of the sequence. 
 
     
     
       6. The image forming device of  claim 4 , wherein
 the standard pattern forming unit forms the first patches and the second patches such that in a direction in which the first patches and the second patches are arranged, grayscale of patches in a sequence of the first patches becomes gradually higher from one end to another end of the sequence, grayscale of patches in a sequence of the second patches becomes gradually lower from one end to another end of the sequence. 
 
     
     
       7. The image forming device of  claim 4 , wherein
 the standard pattern forming unit forms the first patches and the second patches such that all of the first patches have a same grayscale level, and in a direction in which the first patches and the second patches are arranged, grayscale of patches in a sequence of the second patches becomes gradually higher from one end to another end of the sequence. 
 
     
     
       8. The image forming device of  claim 4 , wherein
 the standard pattern forming unit forms the first patches and the second patches such that all of the second patches have a same grayscale level, and in a direction in which the first patches and the second patches are arranged, grayscale of patches in a sequence of the first patches becomes gradually higher from one end to another end of the sequence. 
 
     
     
       9. The image forming device of  claim 3  further comprising
 a developing unit operable to develop a static latent image formed on the image carrier, and 
 a width “de” of the second patches in a secondary scanning direction is either smaller than a distance “Ds” between the image carrier and the developing unit or smaller than a length of a developing area in the secondary scanning direction, wherein the developing area is an area in which during a developing process a developing agent can transfer between the image carrier and the developing unit at a developing position where the image carrier and the developing unit face each other. 
 
     
     
       10. The image forming device of  claim 3 , wherein
 the width “de” of the second patches in the secondary scanning direction is smaller than 2 [mm]. 
 
     
     
       11. The image forming device of  claim 3 , wherein the width “de” of the second patches in the secondary scanning direction is smaller than a width “d” of the first patches in the secondary scanning direction. 
     
     
       12. The image forming device of  claim 3 , wherein the width “de” of the second patches in the secondary scanning direction is smaller than a maximum width in the secondary scanning direction of an image area that is reproduced by the grayscale reproduction method used for reproducing the edge portions. 
     
     
       13. An image forming method for an image forming device that forms an image on an image carrier using a different grayscale reproduction method for each of two or more different attributes contained in portions of the image, the image forming method comprising:
 a standard pattern forming step for forming a different standard pattern on an image carrier in one-to-one correspondence with each different attribute contained in the image portions, wherein the different patterns are each formed using a different grayscale reproduction method used for reproducing image portions containing the attribute; 
 a detecting step for detecting density of each standard pattern formed in the standard pattern forming step; 
 a correction condition setting step for setting, for each different attribute, a condition for correcting grayscale of the image portions containing the attribute, in accordance with the density detected in the detecting step; and 
 a grayscale correcting step performed utilizing a processor for correcting grayscale of the image portions on an image carrier in accordance with each condition set in the correction condition setting step.